What is a Fixed Interval (FI)?
Fixed Interval (FI) means reinforcement is delivered for the first response after a set amount of time has passed.
FI 5-min: The child gets a cookie for asking politely, but only if 5 minutes have passed since the last cookie. Asking 100 times during the 5 minutes gets them nothing.
Characteristics
- produces a Scallop Effect on the graph.
- Behavior is low immediately after reinforcement and speeds up as the time limit approaches.
RBT Practice Exam Scenario
Question: "An RBT looks at her watch. She ignores the client for 2 minutes. At exactly 2 minutes, she looks up and reinforces the next behavior. What is this?"
Answer: FI 2-min.
Think about studying for a test. You don't study at all (low rate) until the night before the test (fixed time), then you cram like crazy (high rate). That is a Fixed Interval scallop.
Frequently Asked Questions About FI
What is the "Scallop"?
It looks like fish scales on the graph. Pause -> Gradual Increase -> Peak -> Reinforcement -> Pause.
Does it key off number or time?
Time. But the learner still has to do the behavior at least once after the time is up.
Is it efficient?
Not really. It produces the lowest rate of responding among the basic schedules because "working harder" doesn't make the time go faster.